Signficance The purpose of this study was to evaluate the sperm surface protein PH-20 as a potential immunocontraceptive vaccine. Objectives In this study, antibody titers following two intramuscular injections of PH-20/MPL-SE were assessed. The development of a contraceptive vaccine could provide safe, effective and convenient birth control for women and men, especially those in developing countries where access to medical care is limited. There were two treatment groups consisting of two females per group. Group 1 received conjugate 1 consisting of PH-20-ovalbumin at 0.52 mg conjugate/0.5 ml conjugate:adjuvant complex, the high dose and group 2 received conjugate 3 consisting of PH-20-ovalbumin at 0.3 mg conjugate/0.5 ml conjugate:adjuvant complex, the low dose. The adjuvant used was MPL-SE (Ribi). Both groups received 0.5 ml of their respective conjugate/adjuvant mix by deep intramuscular injection in both inner thighs at 0.25 ml per site. Injections were done on week 0 and 4 of the study for both groups. Blood (approximately 5 cc) was collected for both treatment groups approximately one week prior to first injection, then on week six of the study. All blood samples were processed for serum and analyzed for antibody titers by Dr. Paul Primakoff. Vaginal wash and cervical mucus samples were collected once during weeks six through eight, with specific collections coinciding with ovulatory surge for each animal respectively. Females were observed as per CRPRC guidelines for menses. In addition, females were checked as per CRPRC guidelines for any localized reactions at the injection sites. Results All blood sera and vaginal wash samples collected were forwarded to Dr. Paul Primakoff for antibody titer analysis. Future Directions Fertility Trial will be conducted in non-human primates to assess contraceptive effectiveness using this antigen and treatment regimen followed by a breeding phase of approximately 4-6 months. KEYWORDS immuno-contraception, sperm antigens, vaccine